//#include <bits/stdc++.h>
#include <fstream>
#include <vector>
#include <bitset>
#include <unordered_map>
#include <algorithm>
#include <queue>
#include <math.h>
#include <iomanip>
#include <stack>
#include <string.h>
#include <set>
 
using namespace std;
 
ifstream in("trie.in");
ofstream out("trie.out");

struct Trie
{
	int apps;
	int word;
	
	Trie *next[30];
	Trie *father;
	
	Trie()
	{
		for(int i = 0; i < 30; i++)
			next[i] = nullptr;
			
		apps = word = 0;
	}
	
	void add(string word)
	{
		Trie *curr = this;
		
		for(int i = 0; i < word.size(); i++)
		{
			if(curr -> next[word[i] - 'a'] == nullptr)
			{
				curr -> next[word[i] - 'a'] = new Trie;
			}
			
			curr = curr -> next[word[i] - 'a'];
			curr -> apps++;
		}
		
		curr -> word++;
	}
	
	void erase(string word)
	{
		Trie *curr = this;
		
		for(int i = 0; i < word.size(); i++)
		{
			curr = curr -> next[word[i] - 'a'];
			curr -> apps--;
		}
		
		curr -> word--;
	}
	
	int find(string word)
	{
		Trie *curr = this;
		
		for(int i = 0; i < word.size(); i++)
		{
			if(curr -> next[word[i] - 'a'] == nullptr)
				return 0;
			
			curr = curr -> next[word[i] - 'a'];
		}
		
		return curr -> word;
	}
	
	int lcp(string word)
	{
		Trie *curr = this;
		
		for(int i = 0; i < word.size(); i++)
		{
			if(curr -> next[word[i] - 'a'] == nullptr || curr -> next[word[i] - 'a'] -> apps <= 0)
				return i;
			
			curr = curr -> next[word[i] - 'a'];
		}
		
		return word.size();
	}
};

Trie *trie = new Trie;

int main()
{
	int op;
	string word;
	
	while(in >> op >> word)
	{
		switch(op)
		{
			case(0):
				trie -> add(word);
				break;
			case(1):
				trie -> erase(word);
				break;
			case(2):
				out << trie -> find(word) << '\n';
				break;
			case(3):
				out << trie -> lcp(word) << '\n';
				break;
		}
	}
}